In this project we determine the antigenic relationships based on VP4 and VP7 neutralization specificities of various rotavirus strains derived from humans and animals. The elucidation of the neutralization specificities of rotaviruses is important in order to achieve a more comprehensive understanding of rotavirus epidemiology and for formulation of an effective strategy for vaccination. Rotavirus G serotypes 1, 2, 3 and 4 have been well established to be of epidemiologic importance worldwide. Recently, serotype G9 has emerged as the fifth most clinically important type of rotaviruses globally. Sequence analysis of the VP7 gene of various G9 isolates has demonstrated the existence of at least 3 phylogenetic lineages. We studied the relationship of the VP7 phylogenetic lineages to the neutralization specificity of nine G9 strains by generating (i) eight (2 lineage 1, 1 lineage 2 and 5 lineage 3) single G9 VP7 gene substitution human x bovine rotavirus reassortants and (ii) hyperimmune guinea pig antiserum raised against each reassortant. We found that antibodies to lineage 1 VP7 neutralized to high titers not only the lineage 1 strains but also the single lineage 2 strain and each of the 5 lineage 3 strains whereas antibodies to the lineage 2 and 3 VP7s were not as efficient in consistently neutralizing the lineage 1 strains. Thus, this study has provided a basis regarding the construction of G9-specific rotavirus vaccine candidates: the VP7 of a G9 strain capable of inducing the most broadly reactive neutralizing antibodies should be utilized for the development of G9-specific vaccine candidate. In addition, in collaboration with the Food and Drug Administration (Chizhikov), we have established an oligonucleotide microarray assay to P genotype human rotaviruses as well as for G genotype other than 1-4 and 9 (i.e., G5, 6, 8, 10 and 12).